Additive for naphthenic acid corrosion inhibition and method of using the same

Abstract

The present invention relates to the field of processing hydrocarbons which causes corrosion in the metal surfaces of processing units. The invention addresses the technical problem of high temperature naphthenic acid corrosion and sulphur corrosion and provides a solution to inhibit these types of corrosion. The three combination compositions are formed by two mixtures separately, with one mixture obtained by mixing compound A, which is obtained by reacting high reactive polyisobutylene (HRPIB) with phosphorous pentasulphide in presence of catalytic amount of sulphur with compound B which is thiophosphorous compound such as phosphorous thioacid ester of Formula (1) and second mixture obtained by mixing compound A with compound C of Formula (2) which is obtained by reacting compound B with ethylene oxide, wherein each of these two mixtures independently provide high corrosion inhibition efficiency in case of high temperature naphthenic acid corrosion inhibition and sulphur corrosion inhibition. The invention is useful in all hydrocarbon processing units, such as, refineries, distillation columns and other petrochemical industries.

The invention claimed is: 
     
       1. A novel additive composition for naphthenic acid corrosion inhibition comprising a chemical mixture of:
 i) a corrosion inhibiting amount of an olefin phosphorous sulphur compound A, and 
 ii) a corrosion inhibiting amount of a compound selected from a group consisting of:
 iia) a thiophosphorous sulphur compound B, and 
 iib) a thiophosphorous sulphur compound C, 
 wherein said olefin phosphorous sulphur compound A is a reaction product of reacting olefin with phosphorous pentasulphide, to form a reaction comprising olefin phosphorous sulphur compound A, wherein a molar ratio of said olefin to said phosphorous pentasulphide is between 1:0.05 and 1:1.5, and wherein said reaction of the olefin with the phosphorous pentasulphide is carried out (a) in multi-step heating, (b) in presence of catalytic amount of sulphur, and (c) under nitrogen as purging, and thereby resulting into said compound A; and 
 wherein said thiophosphorous sulphur compound B comprises a phosphorous thioacid ester of the formula 1 
 
 
       
         
           
           
               
               
           
         
         wherein X comprises at least one of sulphur and oxygen and at least one X comprises sulphur and wherein R 1  and R 2  are selected from hydrogen and hydrocarbyl having 5 to 18 carbon atoms, and includes mono-, di-, mixtures thereof;
 wherein said compound C of formula 2 is obtained by reacting said compound B with an oxide selected from the group consisting of ethylene oxide, propylene oxide and butylene oxide and wherein the formula 2 comprises resulting compound C obtained after reaction of said compound B with said ethylene oxide, and includes mono-, di-, mixtures thereof; 
 
       
       
         
           
           
               
               
           
         
       
     
     
       2. The novel additive composition as claimed in  claim 1 , wherein said olefin comprises polyisobutylene, which is at least one of highly reactive and normal. 
     
     
       3. The novel additive composition, as claimed in  claim 1 , wherein said olefin phosphorus sulphur compound A is arrived at, by stirring and heating said reaction mixture of  claim 1 , to 160° C. under nitrogen gas purging, maintaining said reaction mixture between about 160° C. to about 180° C. for a period of about 1 hour to about 2 hours, raising a temperature of said reaction mixture to from about 185° C. to about 250° C., and maintaining said reaction mixture with said raised temperature for between about 1 to about 24 hours, cooling the reaction mixture to 100° C. and purging nitrogen gas into a reaction vessel to drive out hydrogen sulphide gas, thereby resulting in said olefin phosphorous sulfur compound A. 
     
     
       4. The novel additive composition according to  claim 1  wherein said olefin has between 10 and 1000 carbon atoms. 
     
     
       5. The novel additive composition according to  claim 1  wherein said olefin has a molecular weight of from 200 to 10,000. 
     
     
       6. The novel additive composition according to  claim 1  wherein said olefin has a molecular weight of about 950 to about 1300. 
     
     
       7. The novel additive composition, as claimed in  claim 1 , wherein the amount of said mixture of said compound A and said compound B, which is added to crude oil for high temperature naphthenic acid corrosion inhibition, is from about 1 ppm to about 5000 ppm. 
     
     
       8. The novel additive composition, as claimed in  claim 7 , wherein a ratio of said compound A to said compound B, by weight, is from about 1:1 to about 4:1. 
     
     
       9. The novel additive composition, as claimed in  claim 1 , wherein the amount of said mixture of said compound A and said compound C, which is added to crude oil for high temperature naphthenic acid corrosion inhibition, is from about 1 ppm to about 5000 ppm. 
     
     
       10. The novel additive composition, as claimed in  claim 9  wherein a ratio of said compound A to said compound C, by weight, is from about 1:1 to about 4:1. 
     
     
       11. A process for at least one of naphthenic acid corrosion inhibition and sulphur corrosion inhibition of a metallic surface of any of hydrocarbon processing units, wherein said processing units comprise at least one of a distillation column, a stripper, a tray, a pump around piping, and related equipment, using an inhibitor combination compound selected from a group comprising a mixture of said two compounds A and B, and said two compounds A and C of  claim 1 , comprising the steps of:
 a. heating a hydrocarbon containing at least one of the naphthenic acid and sulphur compound, to vapourize a portion of said hydrocarbon; 
 b. condensing a portion of the hydrocarbon vapours, passing through said hydrocarbon processing unit, to produce a condensed distillate; 
 c. adding to said distillate, before said condensed distillate is at least one of returned to said hydrocarbon processing unit and collected as a product, from about 1 ppm to about 5000 ppm of said inhibitor combination compound, wherein a ratio by weight of said compound A to said compound B is from about 1:1 to about 4:1, and a ratio of said compound A to said compound C is from about 1:1 to about 4:1; 
 d. allowing said condensed distillate containing said inhibitor combination compound, to contact said metallic surface of said hydrocarbon processing unit, to form a protective film on said surface whereby said surface is inhibited against corrosion; and 
 e. allowing said condensed distillate to be at least one of returned to said hydrocarbon processing unit and collected as said product. 
 
     
     
       12. The novel additive composition as claimed in  claim 1 , wherein said molar ratio of said olefin to said phosphorous pentasulphide is about 1:1. 
     
     
       13. The novel additive composition as claimed in  claim 3 , wherein the temperature of said reaction mixture is raised to between about 190° C. to about 230° C. 
     
     
       14. The novel additive composition as claimed in  claim 3 , wherein the temperature of said reaction mixture is raised to between about 210° C. to about 225° C. 
     
     
       15. The novel additive composition as claimed in  claim 3 , wherein said reaction mixture is maintained at said raised temperature for between about 6 and about 10 hours. 
     
     
       16. The novel additive composition, as claimed in  claim 7 , wherein an amount of said mixture of said compound A and said compound B, which is added to crude oil for high temperature naphthenic acid corrosion inhibition, is from about 1 ppm to about 300 ppm. 
     
     
       17. The novel additive composition, as claimed in  claim 9 , wherein an amount of said mixture of said compound A and said compound C, which is added to crude oil for high temperature naphthenic acid corrosion inhibition, is from about 1 ppm to about 300 ppm. 
     
     
       18. The process as claimed in  claim 11 , wherein said inhibitor combination compound in step c) is added to said distillate in an amount varying from about 1 ppm to about 300 ppm. 
     
     
       19. A method of using naphthenic acid corrosion inhibiting composition of  claim 1  for at least one of naphthenic acid corrosion inhibition and sulphur corrosion inhibition of a metallic surface of hydrocarbon processing units comprising at least one of a distillation column, a stripper, a tray, a pumparound piping, and related equipment, wherein the composition consists of a chemical mixture of:
 i) a corrosion inhibiting amount of said olefin phosphorous sulphur compound A, which is produced by reacting olefin with phosphorous pentasulphide in presence of a catalytic amount of sulphur, to form a reaction mixture, with a molar ratio of said olefin to said phosphorous pentasulphide being between 1:0.05 and 1:1.5, and 
 ii) a corrosion inhibiting amount of said compound selected from the group consisting of:
 iia) said thiophosphorous sulphur compound B, and 
 iib) said thiophosphorous sulphur compound C; and 
 
 wherein the method comprises the steps of: 
 a. heating a hydrocarbon containing at least one of the naphthenic acid and sulphur compound, to vapourize a portion of said hydrocarbon; 
 b. condensing a portion of the hydrocarbon vapours, passing through said hydrocarbon processing unit, to produce a condensed distillate; 
 c. adding to said distillate, before said condensed distillate is at least one of returned to said hydrocarbon processing unit and collected as a product, said inhibiting composition; 
 d. allowing said condensed distillate containing said composition, to contact said metallic surface of said hydrocarbon processing unit, to form a protective film on said surface whereby said surface is inhibited against corrosion; and 
 e. allowing said condensed distillate to be at least one of returned to said hydrocarbon processing unit and collected as said product. 
 
     
     
       20. The method as claimed in  claim 19 , wherein from about 1 ppm to about 5000 ppm of said composition is added in said step c. 
     
     
       21. The method as claimed in  claim 19 , wherein a ratio by weight of said compound A to said compound B is from about 1:1 to about 4:1, and a ratio by weight of said compound A to said compound C is from about 1:1 to about 4:1 in said step c. 
     
     
       22. The method as claimed in  claim 19 , wherein said olefin comprises polyisobutylene, which is at least one of highly reactive and normal. 
     
     
       23. The method as claimed in  claim 19 , wherein said olefin has between 10 and 1000 carbon atoms. 
     
     
       24. The method as claimed in  claim 19 , wherein said olefin has a molecular weight of from 200 to 10,000. 
     
     
       25. The method as claimed in  claim 19 , wherein an amount of said mixture of said compound A and said compound B, or of said mixture of said compound A and said compound C, which is added to crude oil for the corrosion inhibition varies from about 1 ppm to about 300 ppm.